A conventional process for the production of metallic rhenium powders is described in both 1) Tribalat S. Rhenium et technetium, Gauthier-Villars, Paris, 1957, and in 2) Davenport W. H., Spelman J. W., Vaeth H. J. Rhenium Chemicals, Cleveland Refractory Metals, 1969. This conventional process is based on the hydrogen reduction of ammonium perrhenate according to the following reaction:2 NH4ReO4+7 H2→2 Re+2 NH3↑+8 H2O↑  (1)
This reaction is carried out in two consecutive steps; the first involving the thermal decomposition of ammonium perrhenate at 300° C. into gaseous ammonia and rhenium oxide (IV);NH4ReO4+3/2 H2→ReO2+NH3↑+2 H2O↑.  (2)
The second step involves the reduction of the formed rhenium oxide, at 1000° C., to produce metallic rhenium according to the following reaction:ReO2+2 H2→Re+2 H2O↑  (3)
A drawback of this conventional process is that it is relatively slow, and has to be interrupted after 2 hours, in the event that the product is required in powder form. In this case, the formed sintered porous metal oxide/metallic intermediate product has to be ground to the required particle size, followed by the further hydrogen reduction of the powder for a few more hours.
Other processes of bulk rhenium production from the prior art include electrolyse, thermal decomposition of rhenium carbonyl or rhenium tri-chloride, or reduction of rhenium hexa-fluoride. These processes from the prior art are described in Chaudron G., Dimitrov O. Monographies sur les métaux de haute pureté, Chapitre 10 Rhénium, p. 235-242, MASSON, Paris, 1972.
Drawbacks from these other processes from the prior art include:                the yielding of sponge like products difficult to handle and requiring post treatment processing, and        toxicity of the by-products (environmentally hostile).        